Process and apparatus for the treatment of well cuttings

ABSTRACT

A method and apparatus for the treatment of well cuttings especially adapted for offshore use provides a conveyor belt moving the cuttings through a preheater for partial drying and then to a high-intensity infrared heating chamber in which all volatile material is expelled from the cuttings at a surface temperature higher than the combustion point of petroleum, so that non-polluting, oil-free cuttings are discharged.

United States Patent Lawhon et al.

- [4 1 Se t. 26,1972

[ PROCESS AND APPARATUS FOR THE TREATMENT OF WELL CUTTINGS [72]inventors: Charles P. Lawhon, Houston; Kenneth 0. Taylor, Pasadena, bothof Tex.; Jerry A. Brock, Commerce,

Calif.

[73] Assignee: NL Industries, Inc., New York, NY. [22] Filed: Dec. 30,1970 1 [21] Appl. 1 10.: 102,630

[52] US. Cl ..263/8 R, 110/15, 263/28 [51] Int. Cl ..F27b 9/24 [58]Field of Search ..263/8, 28; 34/4; 110/15 [56] References Cited UNITEDSTATES PATENTS 3,560,369 2/1971 Rowlandeta1,,. 263/2 8 2,360,257 10/1944Muller et a1. ..34/4

Primary Examiner-John J. Camby Attorney-Delmar l-l. Larsen, Roy F. Houseand Robert L. Lehman I 57] ABSTRACT A method and apparatus for thetreatment of well cuttings especially adapted for offshore use providesa conveyor belt moving the cuttings through a preheater for partialdrying and then to a high-intensity infrared heating chamber in whichall volatile material is expelled from the cuttings at a surfacetemperature higher than the combustion point of petroleum, so thatnon-polluting, oil-free cuttings are discharged.

8 Claims, 7 Drawing Figures PROCESS AND APPARATUS FOR THE TREATMENT OFWELL CUTTINGS This invention relates to the treatment of well cuttingsas produced in rotary drilling operations, whereby the cuttings arefreed from oil by an infrared combustion process.

In the drilling of wells for oil and gas, a volume of sedimentaryformations is removed from the earth to provide the well bore, which issubsequently cased and eventually in favorable cases placed onproduction. The cuttings are substantially always saturated with water,this being the normal state of buried sediments, and will in many casescontain petroleum hydrocarbons as well. Furthermore, the drilling fluidsused in the commonly employed rotary method of drilling are frequentlymerely aqueous, but very often contain oil as part of the drilling fluiditself, either as a continuous liquid phase as in the case of oil basefluids or the socalled invert emulsion fluids, or they may contain oilas a dispersed phase in the form of an oil-in-water emulsion. When suchfluids are used, the cuttings brought to the surface during the courseof the drilling of the well will bear a surface coating or entrainmentcontaining more or less oil, which is generally a petroleum oil notessentially different from the crude oil sought by the well drillingoperation, although generally representing a refined fraction thereof.

When well drilling operations of the type described are carried out onland, disposal of the cuttings is generally no problem. In remotelocalities they may be simply left as part of the landscape surroundingthe well site, and in more urban areas they may be readily trucked to asuitable dump. In the case of offshore drilling operations, however,cuttings disposal represents a substantial problem. The cuttings may notsimply be dumped overboard, except in the infrequent cases wherein theyare quite free of any oil inclusion. To do so would be to create an oilslick with its attendant problems. It is necessary in the general caseto transport the cuttings back to land and to dispose of them there.Moreover, because of the fact that storage space is at a premium onoffshore drilling installations, transporting of the cuttings to landmust be carried out periodically, and may not be deferred until the endof the drilling operation.

An object of the present invention is to provide an apparatus andprocess for the treatment of well cuttings using a compact device whichremoves substantially all of the oil from the cuttings and combusts theoil completely so that clean cuttings are produced which may be safelydischarged into the lake or ocean surrounding the well site, and inwhich the discharges from the apparatus are all essentiallynon-polluting to the environment.

Other objects of the invention will appear as the description thereofproceeds.

In the drawings,

FIG. 1 is a side view of the inventive device, partially cut away,partially in section, and partially schematic.

FIG. 2 is a top view of the working portions of the device of FIG. 1.

FIG. 3 is a vertical section taken through the device of FIG. I as shownby the arrows therein.

FIG. 4 is a vertical section taken through the apparatus of FIG. 1 asshown by the arrows therein.

FIG. 5 is a vertical section taken through the discharge end of thedevice of FIG. I as shown by the arrows therein.

FIG. 6 is a vertical section taken through the apparatus of FIG. 1 asshown by the arrows in FIG. 2.

FIG. 7 is a fragmentary cross section taken as shown by the arrows inFIG. 4, showing a detail of the cuttings turner.

Generally speaking and in accordance with an illustrative embodiment ofour invention, we provide a conveyor belt, which should preferably bemade of metal mesh so as to be heat resistant and yet permit drainagetherethrough, and which is generally horizontally disposed so as to havean input end and a discharge end. Means are provided to dump thecuttings onto the belt at or.near the input end, and the belt iscontinually vibrated at this point so as to facilitate shaking off anywater which may be entrained in the cuttings. The cuttings are thenconveyed by the belt through an optional preheating chamber where theyare heated by infrared radiation which provides a surface temperature atleast as high as the boiling point of water; and they are next conveyedthrough a high-intensity infrared heating chamber where they aresubjected to the action of infrared radiation of sufficient intensity toprovide a surface temperature at the cuttings high enough to combustpetroleum, also subjected to an air draft. We have found 500 F. to beadequately high. This brings about substantially complete combustion ofany oil associated with the cuttings. In this chamber the cuttings arealso turned over so that the combustion process may be complete. Thecuttings are then conveyed to the discharge end, where they maypreferably be sprayed with water so as to reduce their temperature to asafe handling range. The apparatus and process include additionalfeatures and details which have not been included in this brief summary,but which will be taken up in the detailed description which follows.

Turning now to FIG. 1, this shows a base 10 which is provided forconvenience in handling, and which may be of the type commonly referredto in the oil field as a skid base. The apparatus proper is convenientlymounted on base 10 by means of substantially vertical uprights 11, 12,and 13. These uprights carry a generally horizontal frame 14 whichserves to support, through numerous rollers 15, 16, and the like, theupper portion 17 of the conveyor belt. The lower portion 18 of the samebelt is supported as needed by rollers 19, 20, and the like, in theuprights; and the belt itself is maintained in motion by being stretchedbetween two drums 21 and 22, of which the latter is driven by motormeans 23, all of which is of conventional type and need not be describedin detail. The motion is such that the top portion 17 of the belt movesfrom left to right as viewed in FIG. 1 and FIG. 2.

Superimposed upon the input portion of the conveyor belt is a cuttingshopper 24, containing some spreader bars 25 insuring an evendistribution of the cuttings as they fall down onto the conveyor belt17. The hopper 24 and the associated portion of the conveyor belt arevibrated by an electrically driven eccentric vibrator 26 of conventionalconstruction. Water shaken out of the cuttings by this vibrating actionis collected in trough 27 and eventually discharged through dischargepipe 28. The cuttings then move into a preheating chamber 29, where theyare subjected to infrared radiationfrom heating elements 30 which may beof the type of a steel tube containing an electric resistance elementand a heat transmitting, electrically insulating packing such asmagnesium oxide. As mentioned, this serves in large measure to drive offthe surface water from the cuttings, and to dehydrate their interior. Weprefer that these preheating elements 30 be operated at such a rate thata surface temperature of the cuttings beneath them on the conveyor beltreaches at least the boiling point of water.

From the preheating chamber 29, the cuttingsnext pass into and through ahigh intensity heating and combustion chamber 31, in which there aremounted a plurality of high-intensity infrared lamps, most convenientlyof the type comprising a heavy-duty straight filament in a heatresistant tubular envelope. That supplied by the Gerieral ElectricCompany having a quartz tubular envelope 18 inches long, operating at3,200 watts and 384 .volts is eminently suitable. In our preferredembodiment, we provide 18 such lamps in three batteries of six each, asmay beseen from FIG. 6. The lamps 32, 33, etc. are mounted in a housing40 which is provided-with water cooling for the housing proper, and aircooling for the lamps themselves, as may be seen from FIG. 6. Aconsiderably larger amount of air is supplied to the cuttings traversingchamber 31 by the suction in plenum 39, from which air is removed byexhaust duct 34. As may be seen from FIG. 4, this air traverses theconveyor belt downwardly and passes down through the bed of cuttings ontop of the belt, which are simultaneously subjected to intense infraredradiation, so that this combination of air and heat brings aboutthorough combustion of petroleum hydrocarbons entrained in and on thecuttings. The air with all the products of combustion therein is ventedthrough exhaust duct 34, by blower means not shown.

Approximately halfway in the middle of the high intensity infraredheating portion of chamber 31 there is mounted directly on top of theconveyor belt 17 a cuttings turner 35, which as may be seen from FIG. 7is essentially a splined shaft mounted on journals. This turns with theconveyor belt and serves the function of tumbling the cuttings as theypass over the shaft and fall down onto the conveyor belt on thedownstream side of shaft 35.

The cuttings next pass to the discharge end of the belt, where, as maybe seen in detail in FIG. 5, they fall off the belt at its far end andare simultaneously sprayed with coolant water through a sparging tube36, falling into the cuttings discharge hopper 37 and eventually intothe cuttings discharge tube 38.

FIG. 2 is a plan view of the device shown in elevation in FIG. 1, andcalls for no detailed discussion. H6. 2 shows the disposition of theoptional preheating elements 30, which are used when the cuttingsentrain an unusually large proportion of water, or when the device is tobe used at or near maximum throughput.

FIG. 3, as already mentioned, is a vertical section taken as shown bythe arrows in FIG. 1, and illustrates the cuttings input, where theyfall onto the moving conveyor belt, and also shows the excess waterwhich is shaken from the cuttings with the aid of the vibrating means 26and which passes downwardly into trough 27 and eventually is dischargedthrough the water discharge pipe 28.

In the embodiment of our invention which we have described'indetail, wehave shown as the source of the infrared radiation a battery of lampspowered by electricity. While electricity is generally the mostconvenient power source on offshore installations, it is to beunderstood that other sources of high intensity infrared radiation maybe substituted for the batteries of electrically powered lamps. Forexample, there are commercially available catalytic surface combustionheating units powered by natural gas, especially liquefied petroleumgas, in which a large part of the heat of combustion is converted toinfrared radiation. Since these are eminently cleanbuming devices, theyare well adapted to the present invention in situations where theavailability of gas as'the power source is not a problem.

It may be seen that the invention accomplishes its objects, providingnot only for the discharge of clean, substantially oil-free cuttings atthe cuttings discharge tube 38, but also, because of the fashion inwhich air is drawn downwardly over the cuttings while they aresimultaneously subjected to the intense infrared irradiation, providingfor the discharge of the air with the erstwhile petroleum hydrocarbonsfully combusted to carbon dioxide and water vapor. The invention is thusof great value from the standpoint of environmental hygiene.

We wish it to be understood that we do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

Having described the invention, we claim:

1. A process for the treatment of cuttings from rotary well drillingoperations which transforms them from a wet, oily condition to a clean,substantially oil-free condition which comprises the steps of emplacingsaid cuttings on a moving metallic substantially horizontal conveyorbelt; freeing excess water from said cuttings while on said belt;conveying said cuttings to a combustion chamber wherein said cuttingsare simultaneously subjected to infrared radiation of sufficientintensity to produce a surface temperature sufficiently high to combustany petroleum on and in said cuttings while simultaneously pulling airdownwardly through said cuttings while subjected to said infraredradiation; tumbling said cuttings while intermediate of said combustionchamber; discharging said air; and subsequently discharging saidcuttings.

2. The process in accordance with claim 1 wherein said temperature is atleast 500 F.

3. The process in accordance with claim 1 wherein said freeing of excesswater is brought about by vibrator ry action.

a. The process in accordance with claim 1 wherein said cuttings aresubjected to a preheating with infrared irradiation subsequent to saidemplacement on said conveyor belt but prior to said cuttings reachingsaid combustion chamber.

5. Apparatus for the treatment of rotary well drilling cuttingscomprising frame means; metallic conveyor belt means generallyhorizontally disposed and supported by said frame means; motor means fordriving said conveyor belt so that the upper loop thereof moves in asubstantially horizontal direction; input means for receiving saidcuttings and distributing them onto the top of said belt; water-freeingmeans adjacent said discharging substantially oil-free cuttings fromsaid apparatus.

6. Apparatus in accordance with claim 5 wherein said temperature is atleast 500 F.

7. Apparatus in accordance with claim 5 in which said water-freeingmeans is a vibratory means.

8. Apparatus in accordance with claim 5 having water quenching means forsaid cuttings after said cuttings have left said combustion chamber.

1. A process for the treatment of cuttings from rotary well drillingoperations which transforms them from a wet, oily condition to a clean,substantially oil-free condition which comprises the steps of emplacingsaid cuttings on a moving metallic substantially horizontal conveyorbelt; freeing excess water from said cuttings while on said belt;conveying said cuttings to a combustion chamber wherein said cuttingsare simultaneously subjected to infrared radiation of sufficientintensity to produce a surface temperature sufficiently high to combustany petroleum on and in said cuttings while simultaneously pulling airdownwardly through said cuttings while subjected to said infraredradiation; tumbling said cuttings while intermediate of said combustionchamber; discharging said air; and subsequently discharging saidcuttings.
 2. The process in accordance with claim 1 wherein saidtemperature is at least 500* F.
 3. The process in accordance with claim1 wherein said freeing of excess water is brought about by vibratoryaction.
 4. The process in accordance with claim 1 wherein said cuttingsare subjected to a preheating with infrared irradiation subsequent tosaid emplacement on said conveyor belt but prior to said cuttingsreaching said combustion chamber.
 5. Apparatus for the treatment ofrotary well drilling cuttings comprising frame means; metallic conveyorbelt means generally horizontally disposed and supported by said framemeans; motor means for driving said conveyor belt so that the upper loopthereof moves in a substantially horizontal direction; input means forreceiving said cuttings and distributing them onto the top of said belt;water-freeing means adjacent said cuttings input means for excess waterremoval from said cuttings; preheating means adjacent said input means;a combustion chamber surrounding a portion of said conveyor belt andcontaining infrared radiation means irradiating the top of said belt soas to produce a surface temperature of any cuttings thereon of at leastsufficient to combust any petroleum thereon; cuttings turning meansintermediate of said combustion chamber; air exhaust means in saidchamber serving to pull air downwardly through said belt and saidcuttings thereon underneath said infrared lamps; and means fordischarging substantially oil-free cuttings from said apparatus. 6.Apparatus in accordance with claim 5 wherein said temperature is atleast 500* F.
 7. Apparatus in accordance with claim 5 in which saidwater-freeing means is a vibratory means.
 8. Apparatus in accordancewith claim 5 having water quenching means for said cuttings after saidcuttings have left said combustion chamber.